The invention broadly relates to jamb liners for window assemblies, and is specifically directed to a jamb liner usable for slidable closures such as double hung windows and including structure for biasing the jamb liner against the closure member.
The conventional construction of double hung window assemblies includes a jamb liner that is mounted to each side of the jamb to receive and guide the slidable window or sash. Typical jamb liners are extruded from plastic materials such as polyvinylchloride, and are configured with a profile that mates with the sides of the sash for optimum guided sliding movement. Double hung windows are suspended from various types of spring mechanisms that are usually incorporated into the jamb liner. It is also conventional to include some type of spring bias between each jamb liner and its associated jamb to urge both jamb liners into frictional engagement with the sides of the sash, which permits the sashes to be maintained in a desired position. This spring function has been accomplished through various types of spring means, ranging from metal leaf springs to a thickness of resilient polyurethane foam.
These conventional approaches have encountered problems over a period of time insofar that the spring function is concerned. For example, polyurethane foam, which is frequently used in window construction, tends to degrade and become hardened over time due to exposure to air and ultraviolet light. In addition, this approach requires an additional component in the window assembly and therefore increases the cost not only from the standpoint of manufacture but in assembly and installation as well.
Another significant disadvantage is the inability of conventional spring devices to act as a seal against air and moisture. In other words, although the window itself provides such a seal to the primary window opening, it is nevertheless possible for air and moisture to pass through the peripheral space between the jamb liner and jamb. The problem of air and moisture leakage also exists where a backing of resilient foam has been used due to its open cellular structure, although to a lesser extent than conventional spring devices.
A further problem encountered with conventional spring devices, including resilient foam backing, is the inherent linear relationship between deflection and force; i.e., the more the jamb liner is depressed, the greater the resistive force it imparts to the associated sash. Accordingly, if variations occur in the construction, the result can be a sash that slides too easily or with too much difficulty. It is also possible for variations to occur in this biasing force as a function of temperature.
The inventive jamb liner is the result of an endeavor to provide a spring function in a jamb liner that is simpler and potentially less expensive to manufacture and install, and which also provides an effective seal against moisture and air. Specifically, the invention comprises an extruded jamb liner that is provided with at least one longitudinal spring hinge member that projects from the rear or inner face of the jamb liner for engagement with the associated jamb side. Although other manufacturing approaches are possible, the preferred embodiment includes two continuous, elongated spring hinge members that are integrally formed with the jamb liner itself by coextrusion. The hinge member consists of an elongated strip of material the inner or contiguous portion of which is extruded from a resilient, spring like material from a family of thermoplastic elastomers, such as polyurethane or polyester, or blends of such materials, with the extremity of the strip coextruded from the same material as the jamb liner (e.g., relatively stiffer polyvinylchloride). Through coextrusion, the resilient and stiffer portions are simultaneously and integrally formed with the jamb liner into a single unit that simplifies both manufacture and installation. The hinge member, which is flat and blade-like in the first embodiment, is angularly disposed relative to the rear face of the jamb liner, enabling it to be bendably compressed over its length about the resilient portion upon engagement with the associated jamb side. The engagement extends over the entire length of the jamb liner, thus providing both the spring function and a seal against moisture and air.
In the first embodiment, the hinged, flat spring members are disposed identically at the same angle, which facilitates entry of the window assembly into the jamb from one direction (typically from the inside of the window opening). In a second embodiment, the spring hinge members are predominantly flat with curved extremities, and are symmetrically and angularly disposed along the outer edges of the jamb liner.
A third embodiment employs the same structural concept of coextruding resilient and relatively rigid portions to create flexible longitudinal hinge members. However, whereas the first and second embodiments flex in such a manner as to create tensile forces that may become excessive within the resilient portion, the third embodiment is constructed so that flexure results primarily in compressive forces. It has been found that such a configuration resists the incidence of creep (i.e., compression set and lost resilience) in the resilient portion over periods of long use over a wide variety of temperatures. Since creep can result in the loss of resilience, this can adversely affect not only the ability of the jamb liner to properly bias the associated sash, but also the function of sealing against moisture and air.
The third embodiment has a longitudinal hinge member including a resilient portion formed into a small hollow tube or envelope. The hinge member also includes a relatively rigid portion which is predominantly flat, although it may include structural variations along its outer edge to accomplish the desired function in engaging the associated window jamb. It is possible for the hinge member to function satisfactorily with only the resilient tube, but the preferred form includes the relatively rigid flat portion for engaging the window jamb.
It has been found through experimentation with various configurations of the resilient portion that the small enclosed tube or envelope produces a strong, uniform spring force over its length, even under greater and lesser deflections, and also one which remains relatively constant without any significant degree of creep over significant periods of time.
In all embodiments, the coextrusion of the spring hinge members results in a structure that is extremely simple, less expensive to manufacture than the assembly with separate springs, easier to install and long lasting. In addition, the spring hinge members provide an effective and continuous seal against moisture and air over the entire length of the jamb liner, and where two spring hinge members are used, the sealing capability is doubled in addition to providing a uniform spring bias against the sash. Further, all of the embodiments of the improved spring hinge members produce a force upon flexure that is substantially constant over the range of deflection as well as a broad range of temperatures. Consequently, the force imposed by the jamb liners on the associated sashes is essentially constant even with dimensional variations as well as temperature changes. This advantageously permits design of the components to achieve a desired force for optimum sash sliding operation.
The invention is shown embodied in a jamb liner for a double hung window that is not capable of being tilted, but it may be easily adapted to tilt-out windows. The invention may also be adapted for use in a liner that guides a horizontally slidable window or sash, and is not limited to vertically slidable closures.
Further features and advantages will be appreciated from the accompanying specification and drawings.